Reisman SE, Doyle AG, Jacobsen EN. Enantioselective thiourea-catalyzed additions to oxocarbenium ions.
J Am Chem Soc 2008;
130:7198-9. [PMID:
18479086 PMCID:
PMC2574628 DOI:
10.1021/ja801514m]
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Abstract
Asymmetric, catalytic reactions of oxocarbenium ions are reported. Simple, chiral urea and thiourea derivatives are shown to catalyze the enantioselective substitution of silyl ketene acetals onto 1-chloroisochromans. A mechanism involving anion binding by the chiral catalyst to generate a reactive oxocarbenium ion is invoked. Catalysts bearing tertiary benzylic amide groups afforded highest enantioselectivities, with the optimal structure being derived from enantioenriched 2-arylpyrrolidine derivatives.
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